Reciprocating spraying apparatus



March 17, 1959 w. D. GAUTHIER ET AL 2,878,058

RECIPROCATING SERAYING APPARATUS Filed June 1, 1954 2 Sheets-Sheet 2 707/0 valve 10gb 12d 425 TH n .J V a j IN V EN TOR. WILL/AM 0.- GAUTH/El'?HERS'GHEL A WILL/4M5 Attorneys ttes atet H 2,878,058 Patented Mar. 17,1959 RECIPROCATING SPRAYIN G APPARATUS William D. Gauthier and HerschelA. Williams, Indianapolis, Ind., assignors to Ransburg Electro-CoatingCorp., Indianapolis, had, a corporation of Indiana Application June 1,1954, Serial No. 433,514 7 Claims. (Cl. 299-1) This invention relates toapparatus for controlled movement of a spray coating device or the like,and particularly for reciprocating an electrostatic coating device.

Industrial spray coating of articles is well-known. During recent yearselectrostatic forces have been utilized in spray coating systems to moreefficiently effect deposition of spray particles on the articles.Electrostatic coating systems are now in use in which a charged spray ofcoating material particles are projected from an atomizing devicethrough a quiescent atmosphere to be electrostatically deposited on anarticle of manufacture moving on a conveyor past the atomizing device toform a coating thereon. Where the articles to be spray coated are ofsuch length that the entire article cannot be properly coated with astationary atomizing device the eflective width of the spray can beincreased by repetitive or reciprocatory movement of the atomizingdevice transverse to the conveyorized path of the article in order tocoat the entire length of the article.

It has been found that reciprocation of the atomizing device a number oftimes as the article moves past possesses advantages in addition topermitting the coating of larger articles. Such reciprocation permitsthe coating material to be applied to the article in a large number oflight passes or applications which in turn permits a build-up ofunusually heavy films of coating material without a tendency to sag orrun. In some cases it is possible with a reciprocating atomizing deviceto apply the equivalent of two normal thicknesses of coating materialWith a single atomizing device. Moreover, the feature of permitting aslight interval of air drying intermittently with a number of lightpasses is particularly desirable when using certain coating materialssuch as hammertones and metallic paints where too rapid an applicationof such coating materials results in an unsatisfactory finishedappearance. Coating by a number of light passes has the additionaladvantage that any overcoating or other irregularities occurring duringany one pass tend to be covered up or corrected by the other passes.

When a reciprocating atomizing device for the spray coating of articlesis to be used, it has been found desirable to be able to change thelength of stroke and/or rate of movement of the atomizing device withouthaving to first stop the coating operation. For example, it may benecessary to rapidly change the length of stroke of the reciprocatingatomizing device from 70" to 50 and vice versa in order to properly coatintermittent batches of 70" and 50" articles moving along the conveyorinto coating relation with the atomizing device without interrupting thecoating operation or shutting down the conveyor line. Likewise, in orderto accommodate different shapes and types of articles on the conveyorline it is desirable to permit selective control of the speed ofmovement of the spraying device within each stroke without otherwiseinterrupting its cycle of operation.

Due to the use of electrical potentials inthe order of 100,000 volts ormore in electrostatic coating systems, safety requires that any manuallyoperable controls for the system must be mounted a considerable distanceaway from the coating zone and adjacent area wherein portions of theapparatus are at high voltage. Therefore, such controls for areciprocating electrostatic coating device must inherently be remotelyoperable in order to protect the operator.

This invention provides means for changing the length of stroke and/orspeed of a reciprocable spraying device between predetermined limitsduring operation of the coating system. One type of apparatus whichembodies our invention includes a reversible fluid operated motor forreciprocating movement of the atomizing device, a pump for supplyingfluid under pressure to the motor and a reversible two-position valvecontrolling the flow of fiuid from thepump to the motor having oneposition permitting fluid flow to cause movement of the atomizing devicein one direction and another position permitting fluid flow to causemovement of the atomizing device in the other direction. Means areprovided for reversing the two-position valve from one to the other ofits positions by a cam mounted formovement with the atomizing device andat least three cam-operatable control devices each of which is connectedfor operating the valve reversing means only when the control deviceitself is activated. The control devices are arranged for cam operationin accordance with predetermined stroke limits for the atomizing deviceand means are provided for selective activation of one or more of thecontrol devices.

The use of an annular-edged atomizing device in an electrostatic coatingsystem with a generally circularor loop conveyor for moving the articlesto be coated along a curved path to take advantage of the natural spraypattern of the annular-edged atomizing device is shown and described inthe copending application of C. C. Simmons, Serial No. 274,909, filedMarch 5, 1952, now Patent No. 2,808,343. While our invention is in noway limited to such a system, it is admirably adapted for use with anelectrostatic coating system as disclosed in the aforesaid patentapplication. The invention may assume many different forms but forconvenience of illustration there are shown in the drawings and will nowbe fully described several specific embodiments of our invention in anelectrostatic coating system which are illustrative of the principles ofthe invention. However, it will be understood that no limitations are tobe implied from the specific description now provided.

Fig. 1 of the accompanying drawings is a diagrammatic showing of areciprocable atomizing device utilizing one form of the invention;

Fig. 2 is a further diagrammatic showing of another embodiment of theinvention;

Fig. 3 is a front cross-sectional view of a piston block assembly whichmay be embodied in our invention; and

Fig. 4 is a side elevational view of the piston block assembly shown inFig. 3 connected to a pilot valve.

Referring first to Fig. 1, there is diagrammatically shown an elongatedarticle 10 to be coated supported by a support 11 from a conveyor track12. The supported article 10 moves along the conveyor track into coatingrelation with an atomizing device shown generally as 15 which includes arotatable annular-edged atomizing disc 16 Which-is rotated about itsaxis by motor 17 and to which liquid coating material is fed through acentral passageway in the motor and shaft from liquid supply tube 18.Norm-ally the spacing between article 10 and disc 16 is in the order offrom 8 to 12 inches. Article 10 shown is one of an annular series movingaround atomizing device 15 on circular track 12 in the manner describedin the aforesaid co- =of"finely'divided particles of liquid coatingmateriaL- An electrostatic field is established between the'liquid sprayparticles and; the spaced articles to be coated by means of a highvoltage source 19 which is connected -tothe atomizing device whiletthearticles are grounded through conveyor 12 as shown. For the 8 to 12 inchspacingabove mentioned, the potential of thesource 19 may be in theneighborhood of l00,000 volts. Thus, the spray iselectrostaticallydeposited on the article.

Inorde r to reciprocate 'atomizing device transverse to the path ofarticle 10, the atomizing' device is mounted directly or indirectly bycolumn 20 on one end of a piston rod 30. To the other end-of piston rod30 is afiixed -32.-Piston rod 30, piston'31 and cylinder 32 togetherwith their feed lines constitute a fluid motor designated F luid motor33 is operated by a hydraulic fluid and flow of the fluid iscontrolledto effect reciprocation of piston 31 by a compressed air system. It isto be underrelief -valve 42 and through volume control valve 43 so thata controlled quantity of oil is fed'through feed lines -44-and 45 to theupper -end oftcylinder- 32.- Oil is'supplied to the opposite end ofcylinder 32 from feed line 46 after passing through a two positionpilot-operated flow control valve 47 and a variable check orcounterbalance valve48 located between line 44 and line 46. When flowcontrol valve 47 is in position so that liquid isdelivered from feedline 44 to both lines 45 and 46 and thus to both the upper and lowerends of cylinder 32, the dilference in areas between the upper and lowerfaces of piston 31 exposed to the pressure of the hydraulic oil-'(whichdiflerence is equal-to the cross-sectional area of the piston rod) willresult in upward movementof piston 31 and piston rod 30. This in turnwill of-course move atomizing device 15 in an upwardly .direction. Therod, of course, is of a thickness adequate to support the elementscarried by it.

.When valve 47 is in the other of its two positions, liquidfiowto line46 will be cut off. Oil under pressure will,.however,l continue to besupplied at the normal ratethroughline 45 to the upper end of cylinder-32 causing the downward movement of piston SI-and piston rod..30. as-oilis expelled from thelower portion of cylinder J32 andmflows-out throughline 46, counterbalance valve 48, valve 47 and drain lines 50 and 51for. return to. reservoir 40. A vent line 50:: provides atmosphericpressure at the rear-of the piston in counterbalance valve 48 and servesas a path for anyleakage of-toil from the counterbalance valve intodrain line--51.

-Valve 47 is moved from one of its positions to the other. hydraulicallyby oil under pressure through a four-way rotary pilot valve 52. Oilunder pressure is suppliedntovthe pilot valve 52- through a line 54 fromline 4.4.and .the same pump 41 and flow control valves as used tosupplysfluid motor 33. Oil is supplied through line54 to-pilot valve.52Land with the valvein one of its positions theliquid is fed frompilot valve 52 through line-55 tovalve 47 was to move ;valve-47 from oneof its positions-tome other: Whenliquid is thus supplied to valve 47through line 55, a parallel 'line 56 between pilot v-alve' 52"and valve47 is connected through the pilot-valve-toa vent'line 57 and drain line51 to provide atmospheric pressure in the. line and permit any excessoil to drain' back to 'reservoir40; When pilot valve 52 is 'piston'31which is slidably mounted within a cylinder operated or moved into itsother position, liquid under pressure from line 54 is supplied throughline 56 to move valve 47 to its opposite position, in which case line 55is vented through pilot valve 52 to vent line 57 and drain line 51.

The rate of liquid flow to fluid motor 33 through lines and 46 may bevaried to change the rate of movement, i. e. .the speed, of piston 31and piston rod 30 in order to vary the rate of reciprocation ofatomizing device 15 during a predetermined portion of each stroke. Thismay be accomplished lay-providing an additional path of flow for oilfrom pump 41 past pressure relief valve 42 to feed line 44. A line 60feeds a four-way spring-return valve 61 which in turn feeds liquid toline 44 through volume control valve 43a and check valve 63. Volumecontrol valve 43a can be fed selectively through either of two parallellines 64a and 64b containing respectively vcutoff valves 65a and 65b.These speed control lines may be usedin many'diiferent ways. Forexample, liquid can be normally fed to line 44 through volume controlvalve 43 along, that is, normally without any liquid at all flowingthrough.the volume control valve 43a; In such case, cut-off valve 65acould be closed, valve 65b open, and valve 61'normally positioned tofeed liquid to closed'line 64a so that noliquid would flow through valve61. Then if it is desired, for example, to increase the speedof fluid"motor 33, valve 61' would be moved by pressure against its spring intoits other position so that liquid would flow from line 60' through valve61 to the open line 64b, and thence through open cut-otf valve 65a,volume controlvalve' 43a a'ndcheck valve 63 to line 44 to increase'the'oil flow inline 44to the fluid motor.

'Pilotflvalve 52"is actuated, i."e'. moved from oneofits operativepositionsto the" other, by means of' reversing mechanism which can be"selectively changed byremote 'controhfrom one set of limits to anotherwithout interrupting the coating" operation. Means jointly operable withthe reciprocable member, which in theembodimeiit shown is acam bar70afl'ix'ed to piston rod 30, operates the plungers of a plurality. ofspring-return air control valves 71a, 71b, 72a, "72b,"73a' and 73b. Inorder to activate these air control valves compressed air from a source75 is supplied through line'76 to an air supply valve 77. With valve 77open, air flows through lines 78 and 79 to both air control valves 71aand 7112, which operate as a pair. The opening of air supply valve 77also supplies air toline 80 which feeds air supply valves 81 and 82;With'valve'81 open air flows through lines 83 and 84 to both ai controlvalve 72a and 72b which also operate as a pair; likewise, with valve 82open air flowsthrough'lines 85 a'nd'86'to activate the'pair of valves73a and 73b; I i A separate air line runs from each one of air controlvalves '71'a', 7112, 7213,7217, 73a, and 73b to air cylinders 9la',91b,92a, 92b, 9j3a"a'nd 93b respectively. Each of these six air cylinders isarranged to move pilot valve 52 fro'in'one eras 'eperativeposinons totheother. The air cylinders"opei'ate"in pairs corresponding to thepairs' ofair control valves as shown. One effective arrangement of the a'ircylinders in a block assembly for operating pilot valve 52 is shown inFigs; 3 and 4 and will be described in detail hereafter. It has'beenfound that using air cylinders to "operate a 'pilof'valv'e' which inturn hydraulically operatesth'e r'rieaii'sfor'reversing a hydraulicmotor such as nienew comer vzilve '47, 'ismu'ch superior to using'aplurality of compressed aiflines'cirectly connected 16a fidw-r'eversingmeans 's'iichas valve 47. when air supplyva lve 77 "is openand valves81' and 82' rern'ain'blosd it is apparent that only the' pair of aircontrdlvalvesfld'arid 71b. are'activatd, i. e. are able to efiect'a'liangdin thedirectioh'of movement of piston rod 30, an'dt hafaircontifolvalves 72a, 72b, 73a and 73b remain inactive. Thus no changeis produced as the piston rod and "camber remove upwardly andthe end ofthe cam bar passes over and. releases. the spring-loaded plungers ofinactive air control valves 72b, 73b, 73a and 72a in turn, but when thespring-loaded plunger of air control valve 71a moves outwardly as theend of the cam bar moves upward past this valve air will flow from valve71a through the connecting line to move the plunger of air cylinder 91a.The moving plunger of cylinder 91a will trip pilot valve 52 to its otherposition causing a reversal of oil pressures as between lines 55 and 56to reverse the position of valve 47 and thereby cause the downwardmovement of piston rod 30. During downward movement, cam bar 70 willdepress the plungers of the inactive air control valves without effectuntil reaching activated air control valve 71b. Depressing the plungerof this valve causes air to flow through the valve to air cylinder 91bin turn causing reversal of pilot valve 52, valve 47 and fluid motor 33.

The stroke of the piston, and thereby the stroke of atomizing device 15,is under the control of air supply valve 81 or 82. The opening of valve81 will, of course, confine the stroke of the device within limitsdetermined by the pair of air control valves 72a and 72b, while openingof valve 82 will activate air control valves 73a and 73b to confine thereciprocation of the atomizing device to limits determined by thepositions of this latter pair of air control valves. It is apparent thatchanges in the limits of reciprocation can be easily made by adjustingthe positions of the air control valves in relation to cam bar 70.

One such other arrangement of air control valves is shown in Fig. 2. Inthis embodiment allot the pairsof air control valves, and hence thestroke limits, do not lie one within the other as in the embodimentshown in Fig. 1. The coating apparatus, fluid motor, and hydraulicreversing means are all similar to those shown in Fig. 1 and only thenecessary changes in the air control valves will be described. In theembodiment in Fig. 2 compressed air is supplied through line 76 to anair supply valve 77 which when open supplies air to activate air controlvalves 101a and 101k. With only these air control valves activated theatomizing device will reciprocate between limits represented by valves101a and 1011) which, regardless of the other changes in the system,remain as the outer limits of reciprocation.

Air can also be supplied through manually operable air supply valve 81to activate control valves 102a and likewise, air can be suppliedthrough valve 82 to activate control valves 103a and 103b. Appropriateseparate air lines connect each of the air control valves to one of theair cylinders which operate rotary pilot valve 52. Thus when supplyvalves 77 and 81 are open but valve 82 is closed, the atomizing devicewill reciprocate between limits represented by the pair of controlvalves 102a and 10212. When supply valves 77 and 82 are open and valve81 closed the device will reciprocate between limits determined bycontrol valves 103a and 103b. When all of supply valves 77, 81 and 82are open the device will reciprocate between limits determined bycontrol valves 103a and 102b. Various other arrangements of supply andcontrol valves will be apparent to those skilled in the art withoutdeparting from the scope of our invention.

While the supply valves 77, 81 and 82 in both Figs. 1 and 2 are shown asmanually operable, it should be understood that automatic means may beemployed to selectively activate the desired control valves.Photoelectric or other means responsive, either immediately or with atime delay, to diflerences in the size or shape of the articles to becoated moving along the conveyor towards the atomizing device can beconnected to operate one or more of the supply valves and hence theappropriate control valves. In this manner the stroke of the atomizingdevice can be automatically adjusted to permit proper coating of varioussizes and shapes of articles without manual control.

Another feature of the invention provides for selectively changing thespeed cycle of an atomizing device or the like during a given stroke ofits operation without shutting down the system. It may be desired tocoat intermittent batches of two different types of articles, forexample, one type of article may require reciprocation of the atomizingdevice at a constant speed while the other type of article requires afaster speed of the atomizing device through the middle of its strokeand a slower speed near the ends of its stroke. In such a case thehydraulic speed control mechanism may be used with cutoif valve 65aclosed and cut-off valve 65b open as previously described. Thus normallyoil under pressure would flow only through volume control valve 43 toline 44 and such flow, controlled by appropriate setting of volumecontrol valve 43, to fluid motor 33 would move the atomizing device atthe constant rate required for coating articles of the first type justdescribed. Volume control valve 43a wouldbe set to such position thatwhen it received oil throughline64b that the combined flow of oilthrough volume control. valves 43 and 43a would result in the fasterspeed of reciprocation required for the center of the stroke in coatingarticles of the second type described.

To efiect such control a manually operable air supply valve 90 isconnected to supply line to supply air to an additional pair of aircontrol valves 95a and 9511 connected in series with valve as shown.Valve a is normally closed and depression of its plunger opens the valveto permit air to flow to valve 95b which is normally open. Depression ofthe plunger of valve 95b prevents air flow beyond this valve to air line96 and at the same time bleeds line 96 to the atmosphere. Air line 96supplies air to an air cylinder 97 which operates the fourwayspring-return valve 61. Thus when air supply valve 90 is opened toactivate control valves 95a and 95b and when the air circuits in valves95a and 95b are both open, air will be supplied through line 96 to aircylinder 97 for operating against the spring of valve 61 to reverse theposition of valve 61 and change the flow of liquid from closed line 64ato open line 64b. 7

When air supplyvalve 90 is closed so that valves 95a and 95b areinactive, the movement of the plungers of these control valves by cambar 70 Will produce no changes in the speed of fluid motor 33. However,the opening of air supply valve 90 will render the speed controlmechanism operable. Then as cam bar 70 moves downwardly to depress theplunger of valve 95a air will be fed through normally open valve 95b andline 96 to air cylinder 97, operating its plunger and thereby permittingoil from line 60 to flow through line 64b, open cut-ofif valve 65b, flowcontrol valve 43a and check valve 63 to line 44. This will increase thespeed of downward movement of the fluid motor. Then as the end of cambar 70depresses the plunger of control valve 95b which is normally openit will close the valve and release the air pressure in line 96operating the plunger of air cylinder 97. This loss of air pressurepermits the spring operated return of valve 61 to its normal position toshut oil? the flow of oil to volume control valve 43a. This willaccordingly reduce the speed of piston 31 during the remainder of itsdownward stroke. Therefore, by selective opening or closing of airsupply valve 90 the rate of movement of atomizing device 15 can bechanged to accommodate batches of different types of articles movingalong the conveyor into coating relation with the atomizing device.

Our invention is not, of course, limited to speed control within thestroke'between only two predetermined points as shown in Fig. 1. Onlyone (or several) of control valves 95a and 95b might be used to make atwo-stage (or a many stage) speed cycle rather than the three-stagecycle above described. Likewise, appropriate camming mechanism can beused in conjunction with the speed control valve or valves to obtain anentire stroke or portion of a stroke with an infinitely or graduallyvarying speed, if such gradual variation in the speed of the atom- '17izing device is desired to properly coat a particular type ofiai'ticle;

Figs. 3 and f4 illustrate a further feature of our'invention whichprovidessanovel arrangement for a plurality of air cylmders to operate ahydraulic pilot valve. As

-shown rotary pilot valve 52 is mounted on a flange 120 of a base plate121.' The rotatable operating shaft 52a plate 121. In this embodimentpiston block assembly 125 incorporates. four air cylinders anddouble-ended :piston assemblies which permits. its use with as many aseight separate or four pairs of cam operated air control valves forreversing the flow of oil to fluid motor33 It is apparent: that more orless :cylinders and piston assemblies may be incorporated in thepiston'block depending upon the particular needs of:the-system. v

The axes of the cylinders of piston block assembly 125 are arrangedgenerally perpendicularto the extent of shaft 124 and either above orbelow it. Two-of these cylinders 126 and 127 lie one above the otheras'shown in Fig. 3. The cylinders and their associated piston assembliesare similar and hence only the assembly associated with cylinder 127 "isdescribed. 7 The opposite ends of cylinder 127 are closed by a pair ofsimilar end plates 128a and 128k. Threaded holes and appropriateconnections, such as, for example, connections 129a and 12% in endplates 128a and 1281; respectively, provide air tight connections to airlines fromappropriate air control valves, for example, the pair of airvalves 71a and 71b. Slidably mounted within cylinder 127 are a pair ofsimilar pistons 130a and 130k. These pistonslare connected by an axiallypositioned hollow shaft 131 by means of pins 132:: and 13%. The hollowshaft 131 has a longitudinal slot 131a which accommodates the end of apin 124a rigidly mounted on rotatable shaft 124. Appropriate flexiblerings such as ring 133a may be mounted on the pistons to'provideeffective sealing between the pistons and cylinder walls.

In the operation of this apparatus, air pressure applied to the face ofpiston 13Gb through the line from air control valve 71b will force thepiston assembly to the left. This will move pin 124a and shaft 124 in acounterclockwise manner to reverse pilot valve 52 and change thedirection of flow of oil to fluid motor 33 as previously described. Thenas control valve 71b is closed by the return stroke of the cam bar, thepressure against the face of piston 13011 will be released. Althoughthis release of pressure will not move the piston assembly, it

will leave the assembly free to be moved by the application of airpressure in the opposite direction against the face of piston 130athrough the air line connected to air control valve 71a as this valve isopened. Such movement to the right of the piston assembly will move pin124a and shaft 124 in a clockwise direction to cause the reversal of therotary pilot valve and accordingly of the flow of fluid to motor 33.

We claim:

1. In an electrostatic spray coating system, a hydraulicreciprocator'for reciprocating a spraying device comprising a cylinder;apiston slidably mounted within said cylinder; a piston rod connected tosaid piston and extending axially beyond the confines of said cylinder;said cylinder, piston and piston rod forming two separate enclosedchambers within said cylinder on opposite sides of said piston; twoseparate lines to said chambers, each line adapted to supply liquidunder pressure to one of said chambers; a hydraulically operatedreversible twoposition flow control valve in one of said lines, saidflow control valve having one position permitting flow of liquid underpressure to said cylinder to cause movement of said piston in onedirection and the other position permitting release of liquid from saidcylinder to cause movement of said piston in-the other direction; means'inblu'ding pilot valve'for hydraulically reversingsaid flowcontrolvalvefrom one of its positions to the other;

a cam bar connected "tosaid piston rod for movement -therewith; at leastthree air control valves each connected 'to-operate said pilot valve andthereby to reverse said flow, control valve only when said air controlvalve is activated by air under pressure supplied thereto, said aircontrol valves being arranged in a series to be operated in successionby movement of said cam bar; a source of air under pressure; a manuallyoperable on-ofl air supply valve; three parallel lines from said airsource for supplying air under pressure to the two outer air controlvalves 'in'said series and to said manually operable air supply valve;and a'line from said air supply valve for selectively supplying airunder pressure to the intermediate air control valve in said series. I

'2. Meansfor changing the length of the stroke of a piston'rod of 'areciprocable hydraulic motor between two distinct sets of predeterminedlimits, comprising a reversible two-position flowcontrol valveassociated with saidmotor having one position permitting flow of liquidunder pressure to cause' movement of said piston in one direction andthe other position permitting flow of liquid under pressure to causemovement of said piston in the "other direction; 'atwo-p'osition pilotvalve connected to saidflow control valve for hydraulically reversingthe position of said flow control valve; a cam-bar connected with saidpiston rod for movement therewith; two pairs of air control valvesoperated by said cam bar and spaced one-from another along the path ofmovement of said cam bar according to the predetermined limits of thestroke of said piston rod, each of said air control valves beingconnected to be'individually capable of causing the operation of saidpilot valve to reverse the position of said flow control valve only whenair under pressure is supplied'to said air control valve; a source ofair under pressure; two manually operable on-ofl air supply valves eachof which is independently supplied with air under pressure from saidsource; and two parallel lines from each of said air supply valves forsupplying air under pressure simultaneously to one of the pair of saidair control valves.

3. Means for changing the length of stroke of a pistonin a reciprocablefluid-operated motor between two sets of predetermined limits,comprising means for supplying fluid to said fluid motor to move saidpiston, a reversible flow control valve connected to said fluid supplymeans and having one position permitting flow of fluid to cause movementof said piston in one direction and the other position permitting flowof fluid to cause movement of said piston in the other direction, meansfor reversing the position of said flow control valve, moving meansassociated with said piston and mounted for movement proportional to themovement of said piston, two pairs of individually operable controldevices operated by said moving means, each of said control devicesbeing capable of operating said flow control valve to reverse the fluidflow only when said control device itself is activated, said controldevices being spaced one from another for operation by said moving meansaccording to the predetermined limits of the stroke of said piston, andmeans for selectively activating each of said control devices.

4. In a spray coating system having a reciprocating spraying device,means for changing the length of stroke of the spraying device betweenpredetermined limits during operation of the coating system comprising areversible fluid operated motor for reciprocating said spraying device,a pump for supplying fluid under pressure to said motor, a reversibletwo-position valve controlling fluid flow from said pump to said motorhaving one position permitting fluid flow to cause movement of saidspraying device in one direction and the other position permitting fluidflow to cause movement of said spraying device in the other direction,means for reversing said two-position valve from one of its positions tothe other, moving means mounted for movement proportional to themovement of said spraying device, at least three control devicesindividually operatable by said moving means, each of said controldevices being connected for operating said valve reversing means onlywhen said control device itself is activated, said control devices beingarranged for operation by said moving means in accordance with thepredetermined stroke limits of the spraying device, and means forselectively activating each one of said control devices.

5. Means for operating the rotatable shaft of a rotary pilot valvecomprising a pin extending substantially radially from the rotatableshaft, an enclosed cylinder lying with its axis ofiset from said shaftand substantially perpendicular thereto, a pair of pistons slidablymounted within said cylinder, a piston rod connecting said pistons, saidpin engaging said rod whereby movement of said rod and pistons withinsaid cylinder will rotate the shaft of said pilot valve from one of itspositions to the other, air lines connected to the opposite ends of saidcylinder, and means for selectively applying air under pressure throughone of said lines to said cylinder for moving said pistons and pistonrod to operate the rotatable shaft of said pilot valve.

6. In an electrostatic spray coating system having a hydraulicallyactuated reciprocator for reciprocating a spraying means, an arrangementfor controlling the stroke of said spraying means comprising atwo-position flow control valve having a first passageway connected tosaid reciprocator, a supply passageway, a vent passageway, andhydraulically operated movable means for connecting said firstpassageway alternatively to one or the other of said supply passagewayand said vent passageway; means for supplying liquid under pressurethrough said supply passageway to said flow control valve; a twopositionpilot valve; two liquid lines connected between the hydraulicallyoperated movable means of said flow control valve and said pilot valvewhereby movement of said pilot valve from one of its positions to theother will hydraulically operate the movable means of said flow controlvalve to connect the first passageway of said control valve from one tothe other of said supply passageway and said vent passageway; aplurality of control devices each in operative relationship with saidpilot valve for moving said pilot valve from one of its positions to theother and each of said control devices being operated by the movement ofsaid spraying means; and means remote from said spraying means forselectively rendering said pilot valve control devices operable.

7. In an electrostatic spray coating system having a hydraulicallyactuated reciprocator including a piston and cylinder device having arod connected to the piston for reciprocating an electrically chargedspraying device, means for changing the length of the stroke of thepiston rod of said reciprocator during the reciprocation of saidspraying device comprising a two-position flow control valve connectedto said reciprocator and movable from a first position permitting flowof liquid under pressure to cause movement of said piston in onedirection to a second position permitting flow of liquid under pressureto cause movement of said piston in the other direction; a two-positionpilot valve connected to said flow control valve for hydraulicallymoving said flow control valve; a cam bar connected to said piston rodfor movement proportional to the movement of said piston rod; aplurality of control means operable by said cam bar and spaced one fromanother along the path of movement of said cam bar according topredesired limits of the stroke of said piston rod; a plurality of pilotvalve moving devices each operable by one of said cam-operated controlmeans, and each in operative relationship with said pilot valve formoving said pilot valve from one of its positions to another; and meansfor rendering each of said control means operable.

References Cited in the file of this patent UNITED STATES PATENTS2,051,052 Morgan Aug. 18, 1936 2,113,161 Osborne Apr. 5, 1938 2,222,630Pickford et a1 Nov. 26, 1940 2,383,023 Sykes et al. Aug. 21, 19452,658,472 Ransburg Nov. 10, 1953 2,660,978 Dyne et a1. Dec. 1, 1953

